1. Field of the Invention
The present invention relates to a method for the production of n-doped silicon crystals having a dish-shaped profile of specific electrical resistance (.rho.) in a radial direction.
2. Description of the Prior Art
It is generally desirable to produce silicon single crystal rods for the production of semiconductor component elements. Such rods have very even resistance values with respect to radial resistance paths, i.e., the doped-material distribution is provided as homogeneous as possible over the entire cross section of the silicon crystal rod.
Silicon crystals which have a homogeneous specific resistance path .rho. in the disc center and which have a directional increase of the specific electric resistance (.rho.) towards the disc outer margin (dish-shaped .rho. profile of the silicon crystal disc) are desirable for the production of special semiconductor component elements such as large-surface, high blocking power thyristors. In such devices it is desirable to displace the avalanche breakthrough from the disc edge or margin to the disc center. This means that the doping material distribution in the radial direction is lower in the margin regions of a crystal disc than in the center regions.